已知弦长L=70,弧高H=30,求弧长C?弧半径为R,弧所对的圆心角为A.R^2=(R-H)^2+(L/2)^2R^2=R^2-2*R*H+H^2+L^2/42*R*H=H^2+L^2/4R=H/2+L^2/(8*H)=30/2+70^2/(8*30)=35.417A=2*ARC SIN((L/2)/R)=2*ARC SIN((70/2)/35.417)=...